Fracturing in open hole is a complex subject and has been studied and written about by various authors. Whether using explosives or fluid jets one of the problems with the initiated fractures is in the way they propagate. If the propagation pattern is more tortuous as the fractures emanate from the borehole an undesirable condition called screenout can occur that can dramatically decrease the well productivity after it is put on production.
Hydraulically fracturing from any borehole in any well orientation is complex because of the earth's ambient stress field operating in the area. This is complicated further because of the extreme stress concentrations that can occur along the borehole at various positions around the well. For instance, there are positions around the borehole that may be easier to create a tensile crack than other positions where extreme compressive pressures are preventing tensile failure. One way that has been suggested to minimize this condition is to use jets that create a series of fan shaped slots in the formation with the thinking that a series of coplanar cavities in the formation will result in decreased tortuosity. This concept is discussed in SPE 28761 Surjatmaadja, Abass and Brumley Elimination of Near-wellbore Tortuosities by Means of Hydrojetting (1994). Other references discus creating slots in the formation such as U.S. Pat. Nos. 7,017,665; 5,335,724; 5,494,103; 5,484,016 and US Publication 2009/0107680.
Other approaches oriented the jet nozzles at oblique angles to the wellbore to try to affect the way the fractures propagated. Some examples of such approaches are U.S. Pat. Nos. 7,159,660; 5,111,881; 6,938,690; 5,533,571; 5,499,678 and US Publications 2008/0083531 and 2009/0283260.
Other approaches involved some form of annulus pumping in conjunction with jet fracturing. Some examples of this technique are U.S. Pat. Nos. 7,278,486; 7,681,635; 7,343,974; 7,337,844; 7,237,612; 7,225,869; 6,779,607; 6,725,933; 6,719,054 and 6,662,874.
Pulsing techniques have been used in jet drilling or in conventional drilling to pulse the bit nozzle flow as described in U.S. Pat. Nos. 4,819,745 and 6,626,253. Also related to these applications is SPE paper 130829-MS entitled Hydraulic Pulsed Cavitating Jet Assisted Deep Drilling: An Approach to Improve Rate of Penetration. 
Jets mounted to telescoping assemblies have been suggested with the idea being that if the jet is brought closer to the formation the fracturing performance will improve. This was discussed in U.S. application Ser. No. 12/618,032 filed Nov. 13, 2009 called Open Hole Stimulation with Jet Tool and is commonly assigned to Baker Hughes Inc. In another variation of telescoping members used for fracturing the idea was to extend the telescoping members to the borehole wall and to set spaced packers in the annulus so as to avoid the need to cement and to allow production from the telescoping members after using some of them to initially fracture the formation. This was discussed in U.S. application Ser. No. 12/463,944 filed May 11, 2009 and entitled Fracturing with Telescoping Members and Sealing the Annular Space and is also commonly assigned.
The present invention seeks to improve the extent of the fracturing that is accomplished beyond the initial formation perforation that is initiated explosively or with a direct impingement nozzle. This is accomplished with a telescoping assembly that directs jet streams from each stage. As the largest stage extends fully the flow of fracturing fluid to it is cut off and redirected to the smaller stages that it surrounds. In turn as the perforation grows from jet impingement some portion of the assembly can continue to extend to keep the gap distance from the nozzle face to the depth of the perforation to a minimum so as to improve the starting and propagating of fractures.